I am very happy with OpenInkPot on my EZ Reader (Hanlin V3). The 0.2 version has never crashed for me, and I use it every day. There are other EInk devices using FBReader, notably those from PocketBook and Onyx.

FBReader starts from a "reader is right" perspective, and this means that much of the publisher provided styling is ignored. At one time all CSS was ignored, but now some is honored in ePub and it isn't always clear what will be used and what will not. Still, ePub is my preferred format with FBReader.